Headband for a mask



FIG. 1 is a front elevational view of a headband for a mask showing my new design, the broken line showing of the filter mask is for illustrative purposes only and forms no part of the claimed design;

FIG. 2 is a top plan view thereof, the bottom plan view being a mirror image thereto;

FIG. 3 is a side elevational view thereof, the opposite side elevational view being a mirror image thereto; and,

FIG. 4 is a rear elevational view thereof. 

The ornamental design for a headband for a mask, as shown and described. 